1. Field of the Invention
The present invention relates to a method for preparing a graphene oxide/white carbon black/rubber nanocomposite material that is completely peeled off, highly dispersed, and of strong interfacial bond strength and, more particularly, to a method of employing combination of emulsion mixing and flocculation, combination of emulsion mixing and spray drying, or mechanical blending to prepare a graphene oxide/white carbon black/rubber nanocomposite material.
2. Description of the Related Art
In rubber industry, carbon black is the most important reinforcing filler in rubber industry. The application of carbon black, however, is being challenged because the production thereof is completely dependent on the decreasing oil reserves. One of the successful alternatives to carbon black produced from non-oil sources is white carbon black, as referred to as amorphous hydrated silica or silica gel (SiO2.nH2O). It is white, non-toxic, amorphous fine power with a primary particle size of 10-40 nm. White carbon black is porous, electrically insulative, and of large internal surface area, high dispersibility, lightweight, excellent chemical stability, high-temperature resistance, and incombustibility. White carbon black is composed of monomers, dimers, or trimers formed from structural units that consist of the disorder covalent bonds of —O—Si—O—. It can be used as a filler for rubbers, plastics, synthetic resins, and paints. It can also be used as a lubricant or insulating material. White carbon black's ability of reinforcing rubbers is similar to that of carbon black. Especially, white carbon black after surface modification is able to render rubbers with high moduli and low rolling resistance. However, due to the weak interactivity between white carbon black and rubbers, rubbers become much less resistive to wear after being filled with white carbon black. As a result, though styrene-butadiene rubber filled with white carbon black has been widely used in production of tires of passenger vehicles, the utility of white carbon black in production of tires of heavy and construction vehicles is still limited, no more than improving the tear resistance of the tires by filling a small amount of white carbon black therein. In order to broaden the utility of white carbon black, improving the wear resistance of rubbers filled with white carbon black by adding additional fillers has been researched. A common method of improving the wear resistance of rubber is adding an appropriate amount of carbon black in addition to white carbon black. This method, however, usually requires large amount of carbon black, leads to a higher rolling resistance and low tear resistance of the tires, and is not environmentally friendly.
Graphene is a membrane formed from hexagonal lattice of sp2-hybridized carbon atoms. It is a two-dimensional material with a thickness of one or a few carbon atoms. The periodic structure extending in a plane and the nanoscale thickness of graphene makes it a nanomaterial in macroscopic scale. Because of the high theoretical specific surface area (approximately 2630 m2/g), large aspect ratio (larger than 1000), and good mechanical strength (with a Young's modulus of 1060 GPa) of graphene, it is potential to be used for reinforcing polymer materials.
In this invention, white carbon black for filling rubbers is partially replaced with completely peeled-off graphene oxide. In nanocomposite materials prepared from these rubbers, the interpenetration of graphene oxide and white carbon black hinders the self-aggregation of these two fillers, leading to uniform dispersion thereof in rubbers. Such nanocomposite materials retain the good properties of white carbon black (including high moduli and low rolling resistance) and have dramatically improved wear resistance, moduli, and tear resistance. Meanwhile, the nanocomposite materials are superior over traditional materials for their excellent air-impermeability and self-recovery capability that result from the layer structure and self-recovery capability of graphene oxide. The rubber nanocomposite materials reinforced by graphene oxide and white carbon black can be used in tires, rubber sheets, tapes, rubber rollers, conveyor belts, seals, and aerospace parts. Because of the excellent self-recovery capability and crack resistance of graphene oxide, it can be used in self-recovery materials and highly crack resistant materials.